Telecommunications switching systems typically are utilized by business users to place telephone calls within their offices, or to other users, by way of a network of telephone systems and communication devices. Currently, many businesses employ a combination of computer networks and telephone systems. Such businesses are faced with a never-ending series of complex decisions as the businesses grow and evolve. The reason for this is that the increasing demands on both the computer and telephone systems require both of these systems to undergo major upgrades over a period of time, generally with associated significant budgetary impacts.
The traditional recommendation for such business customers is to somehow integrate their voice and data traffic onto one network to simplify the planning and procurement process, especially when considering the impact that video and other wide band communications demands will have on their network transport requirements. This approach regards voice communications as a constantly decreasing percentage of data and video communications, and recommends that the network be designed for the most demanding traffic source to allow for the relatively low bandwidth voice traffic to ride along with it.
Systems also exist which allow off-site workers to access resources over the local area network (LAN); but expensive computer server and data routing arrangements are required to accomplish this. This complex arrangement also is expensive to maintain and continuously update.
Known systems generally propose one of two solutions. One is to utilize a private branch exchange (PBX) system which has a packet data network built into it, along with voice switching apparatus. Another is to upgrade the on-site LAN to a sufficient performance level that the LAN can act as a pathway for communications between multimedia devices and still maintain a reasonable quality of voice service.
Such prior art systems, however, lack an interim migration plan for smaller business customers who have relatively limited financial resources. The absence of such an interim plan begs for a more efficient mechanism to migrate a business to multimedia communications and e-commerce applications economically. The solutions which are provided by the known systems do not allow for a gradual migration to advanced networking techniques for customers with limited resources.
United States patents which are related to the technologies discussed above are Hunter U.S. Pat. No. 4,764,919; Beckner U.S. Pat. No. 4,592,048; Beckner U.S. Pat. No. 4,596,010; Tadamura U.S. Pat. No. 5,537,401; and Minakami U.S. Pat. No. 5,878,117. These patents cover interface and control arrangements to bridge between traditional telecommunications networks and packet data networks, for the purpose of combining the positive aspects of both network types, to provide improved communication solutions for customers.
Other prior art patents cover usage of various LAN protocol enhancements to make the quality of encoded voice messages better, so as to reduce user objections about choppy speech, audible delays and audio distortion. Such techniques include changes to the timing of sending LAN packets, as disclosed in the U.S. Pat. No. 6,064,673 to Anderson. Two other United States patents which are directed to techniques for assembling and disassembling voice packets more efficiently are the U.S. Pat. No. 5,923,655 to Veschi and U.S. Pat. No. 5,526,353 Henley.
Some systems are designed to establish direct links from digital telephone facilities normally used for voice to data network sources. These systems provide for data transmission over existing T-1 and PRI telephone trunks. Two such systems are disclosed in the U.S. Pat. Nos. 5,410,754 and 5,796,742 to Klotzbach. Essentially the disclosure of both of these patents is the same. The solution, however, is simply to take data and transmit it over a voice channel. There is no packetizing of voice information for transmitting that information over a LAN network.
Another solution is proposed in the U.S. Pat. No. 5,892,764 to Riemann. This patent discloses packet switching using the LAN to serve as a communication link for a complete PBX system, which does not use a central switching chassis. This is a solely digital system designed as a substitution for a pulse code modulated (PCM) PBX system. For a business customer having a digital PBX operating with PCM voice, the system of this patent offers no solution, other than removing the PBX and substituting the digital system of Riemann.
Product enhancements have been introduced for customers who desire to continue use of a PBX to transport multimedia information, such as voice data and video. Enhancement products of this type generally include function cards that combine audio and data from both a LAN and wide area network (WAN) interface for switching within the PBX. Three such United States patents for this type of a system are Guy U.S. Pat. No. 5,940,479; Chau U.S. Pat. No. 5,550,906; and Greaney U.S. Pat. No. 5,796,729. The Greaney patent employs cards which are plugged into the back plane bus of a digital PBX. The system, however, requires a variable bandwidth back plane to permit the back plane to be used for voice, data, and control signals.
While the various systems of the prior art discussed above provide a number of techniques for combining LAN data and PCM voice data, none of these systems are directed to the needs of customers who already own a PBX, but want a convenient and inexpensive means to switch (and convert) voice encoded packet data directly between a LAN and PCM data used within the PBX network. It is desirable to provide such a system, which is cost effective and which comprises a drop-in module to make existing PBX voice traffic available to network devices that are capable of sending voice over LANs.
It is an object of this invention to provide an improved voice-over Internet protocol system.
It is another object of this invention to provide an improved apparatus and method to create complete connectivity between devices on a LAN with communications and control channels within the existing telephone system while permitting communication over other wide area networks (WAN).
It is an additional object of this invention to cause an existing digital key or PBX system to be accessible by personal computers and other devices connected to a LAN without requiring changes in the software present in the existing PBX system.
It is a further object of this invention to provide an interface card to allow an owner of a digital PBX system to implement a drop-in replacement of existing telephones, with telephones directly connected to the LAN while continuing to permit operation of the PBX with standard digital key sets.
In accordance with a preferred embodiment of the invention, a system and method are disclosed for adapting a pulse code modulation (PCM) telephone system having a PBX with a back plane bus to transport information to and from an Ethernet data network or LAN. To do this, an Internet protocol card (IPC) is coupled to the back plane bus of a digital PBX system in the same manner as digital key set cards normally used with such a PBX. The IPC includes a plurality of digital signal processors and a digital cross point switch coupled in parallel with the digital signal processors, and with the PBX back plane, for routing PCM voice data to and from the digital signal processors. The digital signal processors are controlled by known algorithms to packetize the PCM voice data coming from the PBX and to de-packetize, into PCM voice data, packetized voice supplied to the IPC card from a port connected to the LAN. Power, timing and control interconnections for operating the Internet protocol card are obtained from the back plane.